1. Field of the Invention.
The present invention relates to a vapor return piping system for a fuel storage and delivery system such as typically found at a gasoline service station. More specifically, the present invention is directed to the provision of an outer, larger diameter secondary containment piping system about an inner, primary fuel delivery piping system and to the utilization of the intersticial space between the inner primary fuel delivery piping system and the outer secondary containment piping system for the return of fuel vapor to an underground storage tank.
2. Description of the related art including information disclosed under 37 CFR Sections 1.97-1.99.
Over the last 40 years, there has been an increasing concern about contamination of the environment, including land, sea and air, with petroleum products, such as gasoline fuel utilized in internal combustion engines in vehicles. Thus, over the last 40 years laws, rules and regulations have been promulgated by state and federal governmental bodies prohibiting contamination of the environment with petroleum products such as gasoline.
In view of these laws, rules and regulations, techniques and systems have been developed for minimizing the escape of gasoline from underground storage tanks into adjacent soil or water and for minimizing the escape of gasoline vapor into the air when delivering gasoline to the storage tank or from the storage tank to a vehicle fuel tank.
With respect to the prevention of soil and water pollution, a number of states require that a gasoline storage tank have secondary containment, namely, a double wall or secondary outer wall around the inner, primary wall of the gasoline storage tank. Also, it is required that piping which normally contains fuel be double layered or have a secondary containment barrier around and about the piping from the storage tank to prevent escape of fuel to and into the ambient environment.
With respect to preventing pollution of the air with gasoline vapor, gasoline vapor return lines have been proposed inside or in conjunction with the piping to and from the underground storage tank.
For example, the Brandt U.S. Pat. No. 3,016,928 discloses a device for extracting fumes from liquid fuel storage containers. The device includes a vapor escape line that extends within an output pipe from an underground storage tank to a pumping island and through a delivery hose and outlet nozzle. Fumes generated by the escape of gasoline from the nozzle outlet to a vehicle fuel tank are returned to the underground storage tank. The tank has a lower pressure in the space above the gasoline in the tank as a result of the drop in liquid level in the tank as gasoline is pumped from the tank, i.e. a drop in head pressure.
This patent also proposes a vapor return line in the tubing or hose extending from the inside of a tank truck to an outlet of the hose placed within the storage tank after a distal end portion of the hose is inserted through a storage tank fill pipe for filling the underground storage tank with gasoline.
In the Mayer U.S. Pat. No. 4,100,758, there is disclosed a vacuum assist fuel system which includes a vapor return conduit which extends from a dispensing nozzle to and through the top wall of an underground fuel storage tank. A valve is provided in this conduit to control vapor flow through the conduit back to the storage tank only when gasoline is being dispensed.
Examples of other prior art patents which disclose separate vapor return lines or conduits to an underground storage tank are listed below:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 3,672,180 Davis 3,863,687 Alquist 3,907,010 Burtis, et al. 4,009,985 Hirt 4,010,779 Pollock, et al. 4,018,252 Burtis, et al. 4,566,504 Furrow, et al. ______________________________________
The Davis U.S. Pat. No. 3,672,180, the Alquist U.S. Pat. No. 3,863,687 and the Pollock et al. U.S. Pat. No. 4,010,779 also teach the provision of a condenser in the vapor return path, such as on the gasoline dispensing island at the gasoline service station, whereby the vapor is first condensed and then returned as a liquid to the underground storage tank.
With respect to protection of soil and water by secondary containment of the underground storage tank from leakage of gasoline from the storage tank, it has been proposed by Total Containment, Inc. of Exton, Pa. to provide a jacketed steel tank having a 100 mil thick high density polyethylene jacket around a U.L.58 steel underground storage tank.
Further, in the Webb U.S. Pat. No. 4,805,444, assigned to Total Containment Inc., there is disclosed a secondary containment system comprising telescoping pipe sections of different diameters installed around a primary pipeline between a gasoline dispensing island at a gasoline service station and an underground storage tank.
Also, general information on underground liquid storage systems can be found in:
1. The Petroleum Equipment Institute publication No. PEI/RP100-87 entitled: "Recommended Practices for Installation of Underground Liquid Storage Systems"; and
2. The American Petroleum Institute API Recommended Practice 1615, Fourth Edition, November 1987 entitled: "Installation of Underground Petroleum Storage Systems."
As will be described in greater detail hereinafter, the vapor return piping system of the present invention provides an improvement over the prior art, separate vapor return pipeline systems referred to above by providing an outer, larger diameter piping system including piping mounted about a smaller diameter fuel delivery pipeline or piping system with a continuous axially extending space established within the piping about the fuel delivery pipeline, and utilizing the continuous space for a vapor return path.
The piping can be clear plastic secondary containment pipe of the type sold by R & G Sloane Manufacturing Co., Inc. of Sun Valley, Calif., or similar pipe sold by Occidental Petroleum, Total Containment, Containment Technologies, Red Thread Smith-Inland, or Omnicron.
The vapor return piping system also includes a connection or termination at the proximal end of the outer piping system to a vapor return opening in an underground storage tank, and a connection or termination at or adjacent the distal end of the outer piping system to a vapor return hose or tubing connected to a gasoline dispensing nozzle.